1. Pyruvate dehydrogenase is a large comples enzyme containing many copies of each of three enzyme called E1, E2 and E3. 2. Pyruvate dehydrogenase(E1) has TPP prosthetic groups. Dihyrolipoyl transacetylase(E2) has Lipoamide prosthetic groups, similarly Dihydrolipyl dehydrogenase(E3) has FAD prosthetic group. 3. Dihyrolipoamide and lipoamide can be interconverted. Lipoamide consists of lipoic acid linked via an amid bond to sigma amino groups of a Lys residue. 4. Hydroxyethyl group derived from pyruvate attacks the lipoamide disulfide, and TPP is eliminated. Dihydroxyethyl carbanion oxidised to acetyle group and lipoamide disulfide is reduced. 5. E2 then catalyses to transfer of acetyle group to CoA to acetyle CoA and dihydrolipoamideE2. 6. Dihydrolipoyl dehydrogenase reoxidizes dihydrolipoamide to complete catalytic cycle of E2. The oxidized E3 contains a reactive Cys-Cys disulfide bond and a tightly bound FAD. 7. Finally, reduced E3 is reoxidized. The sulfhydryl groups are reoxidized by a mechanish in which FAD funnels electrons to NAD+ yielding NADH. Solution 1. Pyruvate dehydrogenase is a large comples enzyme containing many copies of each of three enzyme called E1, E2 and E3. 2. Pyruvate dehydrogenase(E1) has TPP prosthetic groups. Dihyrolipoyl transacetylase(E2) has Lipoamide prosthetic groups, similarly Dihydrolipyl dehydrogenase(E3) has FAD prosthetic group. 3. Dihyrolipoamide and lipoamide can be interconverted. Lipoamide consists of lipoic acid linked via an amid bond to sigma amino groups of a Lys residue. 4. Hydroxyethyl group derived from pyruvate attacks the lipoamide disulfide, and TPP is eliminated. Dihydroxyethyl carbanion oxidised to acetyle group and lipoamide disulfide is reduced. 5. E2 then catalyses to transfer of acetyle group to CoA to acetyle CoA and dihydrolipoamideE2. 6. Dihydrolipoyl dehydrogenase reoxidizes dihydrolipoamide to complete catalytic cycle of E2. The oxidized E3 contains a reactive Cys-Cys disulfide bond and a tightly bound FAD. 7. Finally, reduced E3 is reoxidized. The sulfhydryl groups are reoxidized by a mechanish in which FAD funnels electrons to NAD+ yielding NADH..